The zinc-finger factor Snai1 plays an important role in the down-regulation of E-cadherin expression and in the induction of epithelial-mesenchymal transition (EMT) during cancer progression. In gastric cancer tissues, we noted that Snail is abnormally high expressed and is remarkably associated with the lymph node metastasis. Using a plasmid containing newly synthesized artificial microRNA (amiRNA), we transfected gastric cancer cells to block Snail expression. Both Snail protein and mRNA levels were significantly decreased in stably transfected cells, while protein and mRNA expression of E-cadherin was up-regulated. In addition, migration and invasion potential were significantly decreased after knockdown of Snail.